Water SA

Dependence of long-term annual rainfall trends in South Africa on analysis period: 1921–2022

Andries Kruger — 2025-02-18

The focus of the paper is to address the temporal discrepancies in long-term rainfall trend results in South Africa, by evaluating a systematic range of observation periods over the century-long analysis period of 1921–2022. Available long-term climate projections show that significant parts of South Africa are expected to experience progressively drier conditions, mainly in the west. To assess long- term rainfall trends over the country, historical trends should be determined – the results of published studies for which are not consistent. Arguably the most significant reason for these inconsistencies is the length of analysis period. This study investigates this effect on the magnitude and statistical significance of historical annual rainfall trends over hydrological years, with the data of 94 homogeneous rainfall districts. Trends of annual rainfall were determined for all periods up to 2022, from the 1921–2022 period up to the last 30 years, i.e. 1993–2022. The annual rainfall trends over the longest analysis period show significantly positive trends over most of the central and western parts and significant drying over extensive parts of mainly the far north-east. However, the most recent period (1993–2022) shows significantly drying trends over extensive parts of the west, south and east. Among the main findings is that the change in trends shows a consistent spatial pattern of significant negative change over most of the southwestern half, and mostly significantly positive trends over the north-eastern sector. These results are in large agreement with future rainfall projections, particularly for the western half. Ultimately, the study emphasizes the wide range of long-term trends in South Africa, both spatially and temporally, and the importance of considering a range of historical analysis periods in the detection of long-term rainfall changes. In effect, the eventual results provide increased confidence to predicted future rainfall scenarios.

Occurrence of volatile organic contaminants in tap water due to the use of plastic plumbing pipes

Awadh O. AlSuhaimi — 2025-02-18

In the present era, polymeric pipes have emerged as the replacement for metallic alternatives in constructing water distribution networks within cities or homes, due to their notable flexibility and durability. Nevertheless, there have been increased concerns over the safety of consuming water that has come into contact with polymeric materials. This issue arises from the possible leaching of organic contaminants, either due to plastic deterioration or from biofilms that typically develop within polymeric pipes. These biofilms may act as a source of disinfection byproducts during water and/or system disinfection. The objective of the study was to investigate the presence of volatile organic compounds (VOCs) that could migrate from plastic plumbing pipes into tap water. For this purpose, 50 tap water samples from different houses within the Al-Madinah Al-Munawwarah residential area (Saudi Arabia) were collected and analysed for the occurrence of VOCs; trichloromethane (1,1,1-TCA), dichloropropane (1,2-DCP), 1,2,3-trichloropropane (1,2,3-TCP) benzyl chloride (BC) 2- nitropropane (2-NP) 2,4-dichlorophenol (2,4-DCP), 4-ethylphenol (4-EP), benzene and 2-butanone using CG-MS. The most prevalent compounds were benzene, 2-butanone, 1,1,1-TCA, 1,2-DCP, BC, and 1,2,3-TCP. These were identified in 78%, 76%, 68%, 58%, 50%, and 42% of the samples assessed, respectively. The levels of 1,2,3-TCP, benzene, 2,4-DCP and BC exceeded the allowable limit in 43%, 10%, 8% and 6% of the samples, respectively. The remaining VOCs were within the WHO standards. The analysis of water source samples revealed the presence of BC, 1,2-DCP, and 4-EP in 40%, 40%, and 30% of samples, respectively, with no other VOCs detected. This suggests that these contaminants primarily originate from polymeric pipes used in household plumbing systems.

Feasibility of using metakaolinite for the treatment of coal-mining acid mine drainage: insights into the interaction behaviour and partitioning of inorganic contaminants

Matome Mothetha — 2025-02-18

In this novel study, the efficacy of metakaolinite for the treatment of acid mine drainage (AMD) was evaluated. The optimized parameters included the feedstock dosage and contact time. Experimental results were further explored using inductively coupled plasma–mass spectrometry (ICP–MS), ICP–OES (inductively coupled plasma–optical emission spectroscopy), Fourier transform infrared spectroscopy (FTIR), high-resolution– focused ion beam/scanning electron microscopy (HR–FIB/SEM), energy-dispersive x-ray spectroscopy (EDS), x-ray fluorescence (XRF) and x-ray diffraction (XRD). Optimum conditions were observed to be 45 min of mixing time, ≥10 g·L−1 of feedstock dosage, i.e., metakaolinite, and ambient temperature and pH. The metal content (Fe, Mn, Cr, Cu, Ni, Pb, Al, and Zn) embedded in AMD matrices were partially removed whilst the level of sulphate was significantly reduced. Chemical species removal efficacies were observed to occur in the following sequence; Cr ≥ Zn ≥ Cu ≥ Pb ≥ Mn ≥ Ni ≥ sulphate ≥ Mg ≥ Fe, with the following removal percentages: 100, 91.7, 74.6, 65, 38.8, 37.5, 32.3, 13.8, and 8.3%, respectively. Thus metakaolinite proved to be partially effective in the treatment of AMD emanating from coal-mining processes. Furthermore, to enhance the performance of this technology, a polishing technique needs to be coupled or integrated to further remove residual inorganic contaminants, as well as other forms of modification such as the addition of alkaline agents to synthesize the nanocomposite and increase its alkalinizing capabilities.

Groundwater quality assessment in the Breede area, Western Cape, South Africa

Matjiane Pontsho Makonko — 2025-02-18

Groundwater is an essential part of food and water security. This critical resource must be managed appropriately and used sustainably. This study aimed to assess groundwater quality, suitability for domestic and irrigation purposes, and factors contributing to the groundwater chemistry, in the Breede Water Management Area (WMA), Western Cape, South Africa. Groundwater samples were collected and analysed for major ions such as K⁺ , Mg²⁺, Na⁺ , Ca2+, Cl– , HCO₃ – , NO₃ – , F– , SO₄^2– and physical variables like pH, electrical conductivity (EC), total dissolved solids (TDS), and temperature. Water quality index (WQI), total hardness (TH), South African Water Quality Guidelines (SAWQG) and World Health Organisation (WHO) drinking water quality guidelines were used to assess suitability for drinking purposes. Permeability index (PI), magnesium hardness (MH), sodium adsorption ratio (SAR), sodium percentage (Na%) and graphical representations such as Wilcox and United States Salinity Laboratory (USSL) diagram were used to assess suitability for irrigation purposes. Multivariate statistical analysis and the Piper diagram were used to determine the geochemical processes influencing the groundwater quality. TH and WQI revealed that, overall, groundwater in Breede WMA is soft and suitable for drinking. The irrigation suitability indices showed that groundwater is suitable for irrigation, with the exception of a few sites that are doubtful. The dominating water type in the area is Na-Cl, followed by mixed Ca-Mg-Cl. Multivariate statistical methods revealed that the groundwater is affected by the dissolution of rock salts, calcite dissolution, cation exchange and agricultural activities. The overall groundwater in the Breede Water Management Area is suitable for domestic purposes. Water in the boreholes along the coastal area and Borehole W1 must be treated before domestic and irrigation use. There must be consistent groundwater quality monitoring in Breede to identify changes in groundwater quality.

Monitoring seasonal groundwater storage anomalies using remote sensing

Moreblessing Chinyama — 2025-02-18

Knowledge of the dynamics of groundwater storage is essential in understanding its driving processes and for informed decision-making. This requires data with adequate precision, which can be obtained from insitu observations and remote sensing products. While field-based methods are expensive to conduct in low-income countries, satellite products are relatively cheap and provide near real-time data to monitor groundwater resources. This study analyses the seasonal dynamics of groundwater storage anomalies in Zimbabwe. The study utilised the Gravity Recovery and Climate Experiment (GRACE) satellite groundwater monthly point data spanning January 2011 to July 2017. Ordinary kriging was performed to show the spatial variations of groundwater anomaly levels for individual months. Maps for the dry season from April to October were merged together as well as for the wet season from November to March. The final raster maps showed long-term average groundwater level anomalies for each season. Findings show significant variations in groundwater storage level anomalies within and between seasons. The general pattern is that groundwater storage levels increased from the south to north of Zimbabwe. During the wet and dry seasons of 2015, almost 75% of the country had an increase in groundwater storage. This rapid approach using satellite-derived groundwater data, in comparison to other optical remote sensing techniques, is useful for rapid groundwater assessment and management.

Identification of potential sites for rainwater harvesting structures as an adaptation to drought emergencies in Eswatini

Lungile Senteni Sifundza — 2025-02-18

Water scarcity is a global problem exacerbated by the ever-increasing population and climate change, especially in arid and semi-arid regions. Different water resource management strategies, such as rainwater harvesting, have been proposed and implemented worldwide to combat water shortage. Mapping of the optimum sites where these rainwater harvesting structures can be constructed is very important. The main objective of this study was to map and identify, using GIS, optimum sites for the construction of rainwater harvesting structures (farm ponds, check dams and percolation ponds) for agricultural and peri-urban purposes in Eswatini. The optimum sites were identified by overlaying various thematic layers including land use and cover, slope, runoff potential, soil texture and depth and drainage density using ArcGIS 10.8. A general rainwater harvesting suitability map was produced for Eswatini, then potential sites for different rainwater harvesting structures were identified. The results of the study indicated that all three rainwater harvesting structures have suitable sites where they can be constructed. Check dams have potential sites which cover 22.7% of the suitable area in Eswatini, while farm pond and percolation pond sites covers 19.7% and 65%, respectively. Information on existing structures such as dams and earth dams for water storage may need to be gathered to verify the proposed sites of the rainwater harvesting structures. This study was able to identify new sites where structures can be constructed for rainwater harvesting which can improve water availability during dry seasons. Further evaluation may need to be done before implementation of these structures. Moreover, implementing this is subject to a number of other factors, such as the economy, feasibility studies as well as social implications. However, the results of this study will assist policy and decision makers in planning for potential sites for water storage as an adaptation to drought and climate change.

Social demographic patterns and participation in the Gariep Dam fishery, South Africa, during the Covid-19 pandemic

P.J. Swanepoel — 2025-02-18

The global Covid-19 pandemic resulted in an economic downturn that influenced behavioural and participation patterns of fishing sectors around the world. Monitoring changes in fisheries is essential for understanding their human dimension and informing decision- making for development, conservation and management of fish resources. This study documented and described fishery patterns and participation during the Covid-19 pandemic through roving creel surveys. In addition, due to historic surveys of the recreational and subsistence fishery, it was possible to compare the current patterns to previous results and to show the potential Covid-19 related impacts. Subsistence fishing dominated the fishery, with 94% of 431 regular fishers utilising the resources for home consumption or sale. Compared to historic surveys, a marked decline in estimated recreational fishing was observed, but no significant change was identified in participation patterns of subsistence fishers. This downturn in recreational fishing affected the sociodemographic characteristics of the fishery, where changes in ethnic participation were noted; there was also an increase in the number of unemployed fishers during the pandemic. Utilisation of the fish resources was dominated by subsistence users and 97% of fish caught was for self-consumption or sale. This underlines the importance of fish for subsistence users, who rely on the resource for food or income and could not avoid fishing during the pandemic, as they had no alternative. This study highlights the importance of socio-demographic and participation data on fisheries, to provide scientific advice to policymakers on ideal responses to events such as a pandemic. This evidence of temporal changes in hook-and-line fisheries provides inland fishery authorities the opportunity to develop mitigation measures with greater resilience to cope with future global crises. Lastly, the study emphasises the importance of access to fisheries, especially during times of high regional economic and societal stress.

Temporal trends in fisher catch and effort, and the impact of Covid-19 on inland fisheries: a case study from Gariep Dam, South Africa

P.J. Swanepoel — 2025-02-18

Hook-and-line fishing is commonly used in South African inland fisheries; however, very little quantitative information on catch and effort exists, even though it is essential to advise management of the sector. To provide information towards management of South Africa’s largest impoundment, the Gariep Dam, roving creel surveys were conducted to quantify annual fish harvest and to identify changes in fisher catch, effort and harvest data in comparison to historic data. The surveys were also conducted during the Covid-19 pandemic which presented an additional opportunity to describe fishery dynamics during the pandemic. Randomly stratified sampling was conducted from November 2020 to October 2021, in which catch and effort data of hook-and-line fishers were collected. Two fishery user groups were encountered: recreational and subsistence users were present, but the fishery was dominated by subsistence fishers. There was a more skewed dominance between these fisher groups than what was found during similar surveys in 2007/2008. Catch per unit effort was similar to previous estimates, at 0.51 kg·fisher-1·h-1 (95% CI:0.47-0.54). There was, however, a significant reduction in fishing effort during the sampling period when compared to historic data, and estimated annual total harvest was only one third of what was previously reported. It was also noted that recreational fishers avoided fishing during the Covid-19 pandemic, whereas the subsistence fishers could not avoid fishing as it is their primary means of livelihood. The results of the study suggested that subsistence fisheries provide valuable livelihood support to communities, and serve as an example on what impacts a crisis such as a global pandemic may have on inland fisheries.